Distribution System Design - HV Network

Transcription

1 Electricity Policy Document 282 Issue 6 January 2015 Distribution System Design - HV Network Contents 1 Introduction 2 Scope 3 Definitions 4 HV Network and Distribution Substations 5 Documents Referenced 6 Keywords Appendices A and B Approved for issue by the Technical Policy Panel. All Rights Reserved The copyright of this document, which contains information of a proprietary nature, is vested in Electricity North West Limited. The contents of this document may not be used for purposes other than that for which it has been supplied and may not be reproduced, either wholly or in part, in any way whatsoever. It may not be used by, or its contents divulged to, any other person whatsoever without the prior written permission of Electricity North West Limited. Electricity North West Limited. Registered in England & Wales. Registered No Registered Office: 304 Bridgewater Place, Birchwood Park, Warrington, WA3 6XG

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3 Amendment No. Date 0 Issue 1 Issue and Amendment Summary Brief Description and Amending Action 05/11/99 1 Prepared by: DSD Issue 1 Authorised by: 10/04/00 Minor amendment to to aid clarity 0 Prepared by: MK Issue 2 Authorised by: MK 02/07/02 Updated to new UU Template. Norweb replaced by United Utilities. Updated to latest UU organisation. Inclusion of Pad Mounted & Compact Transformers. New clauses and added. Clarification on use of R Form and latest R Form included. Further definitions added. Figure 1 amended to show Pad Mounted & Compact transformers and clarify the application of overhead line isolation. Section 4 re-ordered. Various modifications to text. Decision tree diagrams added in Appendices C, D & E. 1 Prepared by: P. Leather. Issue 2 Authorised by: 10/03/ /07/ /05/06 Amended to conform with ESQCR Also to define preferred substation types, clarify the restriction on the re-use of unprotected transformers, include the use of ASLs and EFIs. Prepared by: P. Leather. Authorised on behalf of the Standards Steering Group by Paul Whittaker: Issue 2 Updated to new Template. Rules for the maintenance of continuity and availability amended. Tees on underground first-legs no longer permitted. Section on Mixed Networks added. R Form amended. Other re-organisation and clarification. Prepared by: P Leather Approved by the Standards Steering Group and signed on its behalf by Paul Whittaker: Issue 2 Reference to new cost apportionment rules added. Use of additional circuit breakers and remote control/automation to improve performance of circuits with large numbers of customers included. Use of circuit breakers extended to include distribution transformer circuits. Requirements for groups of transformers clarified. Other minor amendments and clarifications. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page i of iii

4 Amendment No. Date 4 Issue 2 Brief Description and Amending Action 02/03/ /04/ /07/ /01/ /06/10 Requirements for the use of Totem Pole transformers and connections for single HV customers clarified. References to P2/5 updated to P2/6. Requirements for the use of live-line jumpers amended. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. Issue 3 Company name changed. Security requirement for primary busbars included. Accommodation for primary type switchgear specified. Ratings of air-break switches clarified. Security requirements for cable closures added. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. Issue 4 R Form revised (sub section 4.1.3). Guidance on treatment of Maximum Capacities (sub-section 4.1.6) added. Requirements for Network Performance (sub-section 4.2) expanded. Other consequent amendments. All new underground mains to be 300mm 2 aluminium (subsection ). Further restriction on the use of radial branches (subsection 4.5.3). Requirements for the sectionalising of overhead lines clarified (sub-sections and ). Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. Issue 5 Practice separated from policy and moved to CP282. Use of teed and looped in new connections clarified. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. Issue 5 Further clarification in the use of teed and looped-in connections. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Simon Rushton. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page ii of iii

5 Amendment No. Date 2 Issue 5 Brief Description and Amending Action 19/01/11 Further amendment to the use of teed and looped connections. Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Paul Whittaker: 3 13/4/11 Issue 5 Subsection brought in from CP282 and expanded. Limit of fault rating of DOEFs emphasised (4.4.5). Prepared by: P Leather Approved by the Technical Policy Panel and signed on its behalf by Paul Whittaker: 4 04/10/12 Issue 5 Subsection (Cable Duties and Sizes) amended to allow use of greater use of mm 2 cable Prepared by: P Twomey Approved by the Technical Policy Panel and signed on its behalf by Paul Whittaker 5 08/08/13 Issue 5 Subsection added to protect transfer capacity of interconnectors between Primary Substations. Prepared by: P Twomey Approved by the Technical Policy Panel and signed on its behalf by Paul Whittaker EPD282 I6 Issue 6 21/01/15 PT EPD282 Page iii of iii

6 Amendment No. Date 0 Issue 6 Brief Description and Amending Action 21/01/15 Subsection added to provide design guidance on Undergrounding for Visual Amenity. This includes clarification of requirements for sectionalising circuits; maximum cable length in an operational section; requirements for test van access. Prepared by: P Twomey Approved by the Technical Policy Panel and signed on its behalf by Paul Whittaker EPD282 I6 Issue 6 21/01/15 PT EPD282 Page iv of iii

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8 DISTRIBUTION SYSTEM DESIGN - HV NETWORK 1. INTRODUCTION The general principles contained within this Electricity Policy Document (EPD) shall be applied to all new work on the 11kV and 6.6kV networks (Network) owned and operated by Electricity North West Limited (Electricity North West). The decision as to whether existing Networks shall be brought into line with this EPD when reinforcements or material alterations are carried out (including asset replacement work and new connections) will depend on individual circumstances and each case shall be actively considered. This document is one of the following suite of documents relating to Network Design. (a) EPD279 - Distribution System Design - General Requirements (b) EPD280 - Distribution System Design - 132kV Network (c) EPD281 - Distribution System Design - 33kV Network (d) EPD282 - Distribution System Design - HV Network (e) EPD283 - Distribution System Design - Low Voltage Network This document shall be read in conjunction with EPD SCOPE This EPD describes the general distribution network design principles, at 11kV and 6.6kV, that shall be used by the staff of Electricity North West Limited (Electricity North West), as service provider, and any Independent Connection Provider. It will assist network designers in discharging their responsibilities for compliance with The Electricity Safety, Quality and Continuity Regulations 2002, Electricity Distribution Licence - Condition 5, The Distribution Code and appropriate safety legislation. These design principles shall be applied to the designs of all new work, but not necessarily retrospectively, beyond the requirements of EPD279, subsection Additional information and guidance are available, in Code of Practice 282, to staff and contractors employed by Electricity North West. 3. DEFINITIONS For the purpose of this document the following definitions apply: ASL CI CML CP Distribution Substation DNO - Automatic Sectionalising Links - Customer Interruptions - Customer Minutes Lost - Code of Practice - HV/LV substation - Distribution Network Operator EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 1 of 10

9 DOEF ENA EPD ER GROND HV IDNO LV NOP RC repair-time risk - HV Drop Out Expulsion Fuse - Energy Networks Association - Electricity Policy Document - Engineering Recommendation - Graphical Representation Of Network Data - a software network design tool, with facilities for the optimisation of network performance - For the purposes of this EPD, 11kV or 6.6kV - Independent Distribution Network Operator - Low Voltage - a voltage less than 1000V - Normally Open Point - Remotely Controlled or Remote Control (according to the context). This may include automation. - the possibility that, in the event of a single fault occurring on the Network, the connection of a customer, or a group of customers is interrupted for a period of time, during which essential repairs are carried out. In defining what constitutes a repair, the breaking or making of overhead line jumpers, for example, is to be considered to be repair work, while the removal or insertion of LV links or fuses is not. Substations & Transformers The Electricity Safety, Quality and Continuity Regulations 2002 define substation as: any premises or enclosed part thereof which contains equipment for either transforming or converting energy to or from high voltage (other than transforming or converting solely for the operation of switching devices or instruments) or for switching, controlling or regulating energy at high voltage, but does not include equipment mounted on a support to any overhead line; The above definition is used in this EPD. Compact and Pad Mounted Transformers, therefore, fall within this definition. Compact Substation Ground Mounted Transformer with Integral HV On Load Isolation by means of either a switch-fuse or circuit breaker with feeder earthing facility and LV fuses, enclosed in one cabinet. The design is NOT enclosed by a fence, GRP or other housing. Pad Mounted Substation Ground Mounted Transformer with Integral HV Off Circuit Isolation and HV and LV fuses, enclosed in one cabinet. The design is NOT enclosed by a fence, GRP or other housing. Unit Substation Primary Substation A Ground Mounted Transformer with individual HV Switchgear and LV Fuse Board all enclosed within a GRP housing, building or perimeter fence. 33/11kV or 33/6.6kV substation with all the equipment enclosed within a building or perimeter fence. For the purposes of this EPD a 132kV/11kV Bulk Supply Point shall be treated within the definition of a Primary substation. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 2 of 10

10 Totem Pole Transformer A pole mounted transformer that is connected via an HV cable and not connected to any overhead conductors. (The support to a Totem Pole Transformer should be regarded in every respect as being a support to an overhead line.) 4. HV NETWORK AND DISTRIBUTION SUBSTATIONS 4.1 General The HV Network shall be developed on the basis of feeders between different busbar sections of the same or different Primary Substations. These shall normally operate open as a radial network. By this means, a first-circuit outage of any one section of primary busbar shall be sustainable at any time, all demand being restorable by switching (including, where necessary, manual switching). Exceptions to this might arise, where individual customers, in order to reduce the cost of their connections, have opted for lower levels of security. Where such an option is granted, the security of connection of other customers shall, nevertheless, comply with this EPD and with EPD279 - Distribution System Design - General Requirements Network designers shall consider the optimisation of network performance, when designing any alteration to, extension of or replacement of network equipment in the HV Network. The procedure, which shall be followed in all cases, is detailed further in subsection All designs shall provide facilities for the connection of mobile generation The Network shall be designed to accommodate faults and planned outages. Particularly in considering fault conditions, it is important to limit the need to check and monitor loading conditions, and the number of switching operations required for restoration. All the load (at the time of the maximum demand, with the network running normally) on any one circuit shall be transferable via no more than two normally open points, between that circuit and (an) immediately adjacent circuit(s). With all other circuits running normally, the transfer of load in this way shall be immediately accommodated without exceeding the distribution rating of the alternative circuit(s). Where distribution ratings are not available, cyclic ratings shall be applied. (In practice, depending on the location of any particular fault, the load transferred may exclude that connected to a single substation, a single operational section of an overhead main line or a single radial branch.) It is undesirable to expand the feeding areas of existing 6.6kV Networks Networks with non-standard voltages (ie other than 11kV or 6.6kV) shall not be extended The design criteria for the provision of a temporary connection shall be the same as for a permanent connection The rules set out in the Distribution Licence concerning the apportionment of the costs of connection and any associated reinforcement shall be adhered to When considering the replacement or refurbishment of assets, it is not always appropriate that this should be done on an entirely like-for-like basis. Accordingly, any such proposal, which for reasons of policy or simple expedient, exceeds the cost of replacement with modern equivalents, requires a specific cost justification and the approval of the appropriate Asset Replacement Manager, Electricity North West. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 3 of 10

11 4.2 Incorporating Network Performance Optimisation into Design In order to minimise CI and CML and the associated disruptive effects to customers the following design principles shall be applied Designs shall generally ensure that no more than 200 customers are disconnected for the repair time of a single cable or overhead line fault Where major work (extension (including new connection), refurbishment, reconfiguration or replacement) on the HV Network is proposed, the benefits of including RC shall be considered. RC shall be included as part of the work, wherever justified by the benefits, whenever any of the following trigger criteria prevail: switchgear is to be replaced or added to the Network; a distribution transformer is to be replaced or added to the Network; an overhead line is to be substantially rebuilt or reconductored; or a group of or more customers is to be connected No HV feeder, operating radially, from a Primary substation shall connect more than 20 customers. For this purpose, the number of connected customers shall include all the end-user customers of any embedded network, including those operated by licensed DNOs, IDNOs and by managers of multiple occupancy buildings, where the end-users connections are individually metered As a general rule, no new proposal shall cause any significant detriment to continuity or availability for the existing customers See also the requirement for the inclusion of RC in subsection Normally Open Points Normally open points shall not be fixed through any individual connection agreement Notwithstanding the requirement of , auto change over on dedicated customer feeders (paid for by the customer) is acceptable, ie if no other customers are connected to these feeders To improve customer security of supply, interconnecting HV circuits have been installed between selected Primary Substations. These interconnectors provide transfer capacity between Primary Substation busbars, typically to be used following the loss of a Primary transformer or transformers. They are not distribution feeders. No new demand connection shall reduce the transfer capability of these interconnectors in either direction. Any exceptions shall be referred to the Network Planning Policy Manager, Electricity North West. For clarity these circuits shall be highlighted as interconnectors on the R form Request for Alteration to the HV System electronic diagrams. 4.3 Interconnection of Single Transformer Primary Sites When technical and financial benefits can be demonstrated, a single-transformer primary substation may be operated, with security provided via interconnection on the HV Network. Such interconnection may be operated in parallel, with suitable protection and tap-change control, or may be normally open, with auto-close. This interconnection shall be subject to the requirements of subsection above. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 4 of 10

12 4.4 Substations Ground mounted unit substations, compact and pad-mounted substations shall be designed and equipped in accordance with ES352 - Distribution Substations. The preferred types of Distribution Substation are as follows: a) Unit Substation; b) Compact Substation; c) Pad Mounted Substation; d) building or chamber provided by a developer. For each new substation to be installed, one of these types shall be used, unless Local Authority Planning or other restrictions dictate otherwise. Where the choice of substation type is influenced by a customer or developer, account shall be taken of future maintenance costs. Pad-mounted substations are intended for use in low load density rural and semi-rural situations. It is intended that such installations should not be fenced The standard of accommodation for certain equipment designed only for use indoors, shall comply with the appropriate sections of CP351 - Civil Design aspects of Primary Substations and ES366 - Heating and Lighting Installations in Primary Substations. In particular, temperature and humidity control shall be provided. This requirement shall not be compromised by any power transformer being accommodated within the switchroom, since then ventilation would be required for cooling. In order to limit battery size, any switchgear shall preferably be specified with 30V DC auxiliaries, rather than 110V (notwithstanding the preference for 110V in ES313). In such cases, the design of any protection scheme shall be approved by the Protection Policy Manager, prior to the manufacture of switchgear. Typical equipment requiring this standard of accommodation is as follows: switchgear, generally complying with ES kV and 11kV Single Busbar Indoor Switchgear (Cable Connected); certain protection relays; batteries and chargers; and pilot-cable terminations Where, in order to provide the necessary functionality of switchgear or protection, it is necessary to use switchgear generally complying with ES kV and 11kV Single Busbar Indoor Switchgear (Cable Connected), each panel, except any connecting only local transformers or single customers, of such switchgear shall be equipped with RC with the same functionality, as if the switchgear formed part of a primary switchboard Transformers in urban and suburban locations frequented by the general public, for example on housing estates, shall be ground-mounted. The risks associated with polemounted equipment in such environments are unacceptable. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 5 of 10

13 4.4.5 A totem pole transformer shall be used only where a suitable ground mounted installation cannot reasonably be accommodated, eg in rural and semi-rural locations, where other safety risks and environmental impact are acceptable. A written justification, which shall include a risk assessment covering safety, quality of supply and environmental aspects of the design, shall also be prepared. It is recognised that similar risks will apply to totem pole transformers as to transformers mounted on overhead line supports. It shall also be noted that DOEF mounts are not rated for live operation where the fault level exceeds 7.88kA Pole mounted transformer installations shall be designed and equipped in accordance with current practice Switchgear The use of ground mounted circuit breakers shall be limited to the control of: - (a) All HV circuits directly from Primary substation busbars. (b) Feeder circuits which require additional types of protection. (c) Connections to certain customers metered at HV. (d) Overhead line Networks where ground mounted auto-reclose facilities may be incorporated, see EPD321. (e) Breaking up feeders as might be required by subsection (f) Distribution transformers. Where a circuit breaker is used for this purpose, the 15m maximum length of cable, referred to in does not apply The use of pole mounted reclosing equipment shall be as described in EPD321 - Automatic Reclosing of Overhead Lines Where a recloser cannot be used as a point of isolation, an adequately rated disconnector shall be provided on the normal feed side immediately adjacent to the recloser A switchfuse shall not be used except to protect a single ground-mounted transformer. In this arrangement, the length of HV cable between the switchfuse and the transformer shall be kept to a minimum and shall not exceed 15m Transformers The maximum 11kV/LV or 6.6kV/LV transformer size to be installed or adopted for use on the Network shall be 1000kVA Each 11kV/LV or 6.6kV/LV transformer in a substation shall have its own means of protection at HV and at LV. Where this protection is remote from the transformer, a local load-breaking, fault-making device shall provide a means of isolation. 4.5 Cable Networks A typical HV underground network arrangement is shown in Figure A1 - Appendix A Cable Duties and Sizes All new cables shall be suitable for 11kV non-effectively earthed working. Care shall be exercised in designing HV Networks to ensure that cable duties are within their safe working ratings. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 6 of 10

14 Aluminium cored cable, having a cross-section of mm 2, may be used for any of the following, where the fault level throughout its length is not expected to exceed 9kA, taking into account any reasonably foreseeable reinforcement a) a new connection to or from an overhead line, or where an overhead line forms part of the circuit between points of isolation, provided that the current rating of the cable does not limit the rating of the circuit; b) a new connection between a transformer and its local switchgear; c) a short - less than 100m - diversion or repair, of a cable with an equivalent or smaller current rating. d) for 11kV networks, a connection to switchgear where the composition of the existing circuit is predominately mm 2 Al / 0.06in 2 Cu or less and where the switchgear tails are less than 30 metres in length or e) for radial 11kV networks and circuits that do not form any interconnection between primaries, asset replacement of small section cables of 0.04in 2 Cu or less where it can be demonstrated that the current carrying capacity and voltage performance of the mm 2 cable under normal and abnormal conditions is adequate to provide all supplied domestic customers with a simultaneous maximum demand of 6kW. However, all other new cables shall have a cross-section of 300mm 2 aluminium New HV Connections Except as prohibited by below, a single cable, connected as a tee, shall be used to connect: a) a substation with only one HV end-user customer, unless the customer is to pay the additional cost of a switched alternative connection; b) a pad-mounted or compact transformer, where the number of customers, at repairtime risk, is not expected to exceed 200; or c) any other distribution substation, where the number of customers, at repair-time risk, is not expected to exceed 200 and where the distance to the substation from the point of connection on the existing Network, measured along the proposed cable route, exceeds 2m. Nevertheless, account shall be taken of EPD279, subsection Accordingly, duplicate connections shall be used to connect a new substation: a) such that the two cables are laid in a common trench not exceeding 2m in length (loop-in);. b) where, because of the loading of the Network, the two cables need to take different routes, such that the total length of excavation for the installation of new cable would not exceed 2m; or c) where otherwise the number of customers at repair-time risk is expected to exceed 200. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 7 of 10

15 The transformers connected between points of isolation shall be limited to a maximum of five transformers (pad-mounted and compact added together). The number of customers expected to be connected via a radial branch and at repair-time risk shall not exceed No new radial teed branch shall be connected to the first cable section directly connected to a primary substation. This takes into account the current designs of primary switchgear, which do not permit work on the busbars, with the circuits live. Any proposal for an interconnected teed branch connected to a first cable section from a primary substation shall take account of busbar outages Interconnected Tees Not more than four addresses (not counting pole-mounted transformers and padmounted substations), connected via continuous underground cable, shall be involved in an interconnected circuit. Thus, an underground circuit may have a maximum of four interconnected ends, or three interconnected ends and one radial branch. 4.6 Overhead Networks A typical HV overhead network arrangement is shown in Figure A2 - Appendix A All work on overhead lines shall be planned in accordance with EPD Distribution Networks designed for rural areas shall make full use of automatic reclosing as laid down in EPD321 - Automatic Reclosing of Overhead Lines, and designed to cover as much of the overhead Network as practicable No more than 20km of total HV line length, including radial branch lines, shall be included in any one protection zone Overhead Networks shall be designed to facilitate live line working methods for construction and maintenance and thereby reduce CML Approved live-line connectors, in accordance with ES400O2 and ES400O3, shall be used to facilitate the maintenance of pole-mounted switchgear, ie reclosers and oilimmersed sectionalisers. Consideration shall be given also to the use of approved liveline connectors for cable terminations and other items of plant where there is a significant benefit Main Lines A line (or part of a line) shall be considered to be a main line, if it is interconnected, ie switching enables it to be energised from either end, via different primary substation circuit breakers. All main lines shall be divided into an appropriate number of operational sections, by fully rated load-breaking fault-making switchgear Connections from main lines protected by auto-reclose schemes (See EPD321.) shall be via load-breaking fault-making switchgear, ASLs or DOEF mounts fitted with solid links. Connections from other main lines may alternatively be via DOEF mounts fitted with fuses No operationally continuous part of a main line (albeit that such a part might include one or more sections with jumpers) may have more than seven ends. For this purpose an end is a recloser, a sectionaliser, a switch, a set of links or fuses, or a solidly connected transformer. A branch, within an autoreclose scheme, controlled by a sectionaliser or ASLs within one span of the tee-off position, may be discounted. For example, this would permit a length of line between two switching points, with up to five transformers, connected via solid links. EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 8 of 10

16 For the purposes of and , each operational section of a main line shall include any branch, which connects only one transformer The total route length of each operational section shall not exceed 5km The connections within each operational section shall be limited to a total of 200 customers at repair-time risk and 0kVA of transformer capacity (aggregate name-plate rating) Radial Branch Lines A line shall be considered to be a radial branch line, if it may be energised from only one point and connects more than one transformer. All radial branches shall have means of isolation as close as practicable to their origins and be divided into an appropriate number of operational sections. Switching points between operational sections shall be positioned such as to optimise CI and CML, through the use of a suitable design tool Pole mounted transformers connected to radial branches shall be connected without local means of isolation, unless such means of isolation includes ASLs, deployed as part of an auto-reclose scheme. Radial branches not forming part of an auto-reclose scheme shall have group-fusing applied as close as practicable to their origins No operational section of radial branch shall be more than 5km total route length No operationally continuous part of a radial branch (albeit that such a part might include one or more sections with jumpers) may have more than seven ends. For this purpose an end is a recloser, a sectionaliser, a switch, a set of links or fuses, or a solidly connected transformer, and includes the source end. A sub-branch, within an autoreclose scheme, controlled by a sectionaliser or ASLs within one span of the tee-off position, may be discounted. For example, this would permit a length of line between two switching points, with up to five solidly connected transformers The number of customers at repair-time risk directly connected to an operational section shall not exceed The transformer capacity (aggregate name-plate rating) directly connected to an operational section shall not exceed 0kVA When making a connection to a 3-wire line every effort shall be made to balance single phase loads. The decision shall take into account the existing distribution of connections Remote Control Where the requirements of subsection are satisfied, remote control shall be installed Undergrounding for Visual Amenity Electricity North West may replace parts of an overhead network with underground cable for visual amenity reasons, typically in Areas of Outstanding Natural Beauty and National Parks. The design of such replacements shall take into account the performance and operability of the network, in particular: a) the requirements of apply 21/01/15 EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 9 of 10

17 b) Network shall not be made non-compliant with the requirements of and 4.6. Where any existing network is not in line with the requirements of and 4.6.8, consideration shall be given to making the network fully compliant as part of the undergrounding scheme. c) The maximum aggregate length of underground cable in an operational section shall be 3km. Any exceptions to this rule shall be referred to the Policy and Standards Planning Policy Manager d) Where pole mounted transformers become cable fed, consideration shall be given to relocating the pole to facilitate access with Electricity North West s fault location and test van. Typically this will be within 40 metres of a roadway or metalled drive and preferably have sufficient space to park a test van and generator without impeding access. 21/01/15 e) Consideration shall be given to installation of additional air break switches or suitable overhead line arrangements to sectionalise main lines. Where possible remote control shall be fitted to newly installed devices f) Consideration shall be given to installing additional links or fuses on radial branch lines to provide additional isolation facilities. 4.7 Mixed Networks A typical HV mixed network arrangement is shown in Figure A3 - Appendix A Where circuits comprise mixtures of underground and overhead sections, the general principles outlined in sections 4.5 and 4.6 apply. In particular, circuits shall be divided into operational sections, by fully rated load-breaking fault-making switchgear, ASLs or DOEF mounts fitted with links or fuses, as appropriate, such that the number of connections within an operational section shall be limited to 5. The aggregate number of customers at repair-time risk connected within an isolatable operational section shall not exceed 200. The aggregate transformer capacity (aggregate name-plate rating) connected within an isolatable operational section shall not exceed 0kVA Where a length of overhead network fed from a predominantly underground network exceeds 2km in aggregate (excluding any cable closures) the line shall be separately protected Not more than four addresses (not counting pole-mounted transformers and padmounted substations), shall be involved in an interconnected circuit. Thus, a mixed circuit may have a maximum of four interconnected ends in ground-mounted substations, or three interconnected ends and one radial branch Where sections of overhead line are replaced with underground cable for visual amenity, principles described in section shall apply. 21/01/15 5. DOCUMENTS REFERENCED Non-Electricity North West Documents The following documents, legislation and ENA publication, cannot be supplied by Electricity North West to external parties: Electricity Safety, Quality and Continuity Regulations 2002 ENA Engineering Recommendation P2/6 - Security of Supply EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 10 of 10

18 Electricity North West Published Documents Distribution Code Electricity Distribution Licence The following documents are available from Electricity North West: Distribution Safety Rules - Issued only to Authorised Persons EPD279 - Distribution System Design - General Requirements EPD280 - Distribution System Design -132kV Network EPD281 - Distribution System Design - 33kV Network EPD283 - Distribution System Design - Low Voltage Network EPD321 - Automatic Reclosing of Overhead Lines EPD473 - Policy for Overhead Line Standards - Design, Construction, Refurbishment, Selection and Classification ES kV and 11kV Single Busbar Indoor Switchgear (Cable Connected) ES352 - Distribution Substations ES400O2 - Overhead Lines of Compact Covered Construction for 11/6.6kV: Design& Construction ES400O3 - Bare Wire Overhead Lines on Wood Poles: Design & Construction The following document is available to Electricity North West staff: CP282 - Distribution System Design - HV Networks 6. KEYWORDS Design; Network; Planning; Policy; System; 11kV; 6.6kV EPD282 I6 Issue 6 21/01/15 PT EPD282 Page 11 of 10

19 APPENDIX A EPD282.doc Issue6 21/01/15PTEPD282 Page A1 of kV 33kV 3. Customers Max 2000 per circuit (4.2.1) 2. Radial Tee Single substation with single customer (except during development) or all pad and compact: Max 200 customers Max 0kVA ( ) 0 1. U ground Cable Largest size cable for all new work ( ) No radials (4.5.3) 5. Complexity Max 4 addresses Max 1 radial (4.5.4) /6.6kV M 6. Radial Tee Max 1 T-joint between ring switches ( ) 33kV 11/6.6kV 11/6.6kV Transformer Rating Max 1000kVA ( ) 300 RC RC RC Remote Control Include with any new work on circuit, if justified by benefits - customer numbers. (4.2.2) 4. Radial Tee with Pad and Compact S/Ss Max 5 substations Max 200 customers Max 0kVA ( ) New Substation with RC If > 200 customers, RC on both switches. (4.2.2) Figure A1 - Typical HV Underground Network Arrangement

20 100SCA EPD282.doc Issue6 21/01/15 PT EPD282 Page A2 of 3 11/6.6kV 200 ASL R 33kV 17. Remote Control of NOP Include with any new work on circuit, if justified by benefits - customer numbers. (4.2.2; ) 13. Group Fusing For spur line not part of auto-reclose scheme ( ) 12. Main Line Section Max 5km (excluding radial branches) ( ) Max 200 customers Max 0kVA transformer aggregate rating ( ) 14. PMT Fusing On main line without autoreclose ( ) 11/6.6kV kV 25 RC SCA Radial Branch Section Max 5km ( ) Max 200 customers ( ) Max 0kVA transformer aggregate rating ( ) Live-line Connectors For all PMTs on radial branch lines (4.6.6) Single-phase Loads To be as balanced as possible (4.6.9) 11. Protection Zone Max 20km (4.6.4) Figure A2 - Typical 11/6.6kV Overhead Network Arrangement

21 100SCA 70 EPD282.doc Issue6 21/01/15PTEPD282 Page A3 of kV 33kV 11/6.6kV 200 R 21. Main Line Connection Via switchgear, DOEF mounts, with links or ASLs ( ) 18. Remote Control of NOP Include with any new work on circuit, if justified by benefits. (4.2.2; ) 23. Single Circuit Risk Max 1MW group demand ( ) 11/6.6kV RC RC SCA 100SCA ASL GVR Point of Isolation 20. Where economically practicable (4.7.6) 22. Complexity Max 4 s/s addresses, excl. PMTs and pads (4.5.4) Max 1 radial ( ) Isolatable Section Max 5km o/h Max 200 customers Max 0kVA transformer aggregate (4.6.8) Figure A3 - Typical 11/6.6kV Mixed Network Arrangement